Method of isomerizing butene-1 to butene-2

ABSTRACT

BUTENE-1 IN A MIXED STREAM CONTAINING ISOBUTENE IS ISOMERIZED TO BUTENE-2, BY PASSING THE MIXTURE OVER A STRONTIUM-NICKEL PHOSPHATE CATALYST AT A TEMPERATURE OF 150-440*C.

United States Patent Ofice.

3,830,870 Patented Aug. 20, 1974 3,830,870 METHOD OF ISOMERIZINGBUTENE-l TO BUTENE-Z Mark A. Harter, deceased, late of Midland, Mich.,by Jo Ann Hatter, executrix, Midland, Mich., and John R. Frost, andRobert A. Stowe, Midland, assignors to The Dow Chemical Company,Midland, Mich. No Drawing. Filed Mar. 5, 1973, Ser. No. 337,939

Int. Cl. C07c 5/22 US. Cl. 260-683.2 7 Claims ABSTRACT OF THE DISCLOSUREButene-l in a mixed stream containing isobutene is isomerized tobutene-2, by passing the mixture over a strontium-nickel phosphatecatalyst at a temperature of 150-440" C.

BACKGROUND OF THE INVENTION Butene-l (b.p. 6.3 C.) and isobutene (b.p.-6.9 C.) can be found in hydrocarbon streams from several sources, e.g.,petroleum cracking efiluent streams for producing gasoline or naphthacracker efiiuent streams which also contain ethylene and propylene. Eachof butene-l and isobutene is a desirable raw material, the former fordehydrogenation to butadiene and the latter for preparing aromaticalkylate useful as a gasoline component or for preparing octanes bycontrolled dimerization. However, because of the closeness of theboiling points of butene-l and isobutene, separation by distillation isex tremely difiicult. Other physical separating means are uneconomical,as are chemical separations which depend on conversion of the olefinicunsaturation to form derivatives, e.g., hydration to alcohols,halogenations, etc. A procedure which will alter the physicalcharacteristic of one component of the olefinic C mixture withoutappreciable change in chemical structure to permit separation bydistillation is a novel solution to the problem.

It is to be understood that the isomerization reaction istime-temperature dependent. At comparatively low temperatures of about150 C., a low space velocity (STP) or high retention time is needed toattain appreciable conversion. At comparatively high temperatures, thespace velocity should also be high, i.e., the retention time should below to attain optimum conversion and selectivity of the reaction. Thus,a preferred temperature range is from about 260 to about 410 C. at aspace velocity of from about 175 to about 225 and a more preferredtemperature range at this above indicated space velocity is from 325 toabout 400 C.

SUMMARY OF THE INVENTION It has been found that if a mixture of l-buteneand isobutene is passed over a strontium-nickel phosphate catalyst at atemperature of 260-440 C., preferably 300- 400 C., and a space velocityof 25-800 v./v./h. (STP), without need for steam, oxygen or otherreactant, l-butene is isomerized to a mixture of cis and trans 2-butene(hp. 3.6 and 0.9 C., respectively) while the isobutene remainssubstantially unchanged under these conditions.

The 2-butenes thus can be separated from the cooled reactor efiluent bycareful fractionation. Steam or other diluent is not needed, but if oneis added to the l-butene isobutene mixture entering the reaction, itshould be inert under the conditions of the reaction.

At a temperature of about 235 C. and a space velocity of about 190(STP), isomerization is detectable but conversion of l-butene to2-butene is low. Below about 235 C. at this space velocity,substantially no isomerization of l-butene occurs. At temperatures aboveabout 440 C., the feed mixture tends to undergo considerable cracking,as evidenced by increasing methane production.

The space velocity can range from about 25 to about 800 v./v./h.calculated at STP.

Pressure, per se, seems to have no elfect on the isomerization so thatsubatmospheric, atmospheric or superimposed pressures can be employed.Preferably, the process is operated at autogenous pressure. However, itis possible to control space velocity by controlling pressure, andtherefore this means of space velocity control can be used if desired.One unusual feature of this invention is that under the operatingconditions described, there is extremely little dimerization ortrimerization of isobutene. Typically, the polymerization of isobuteneis less than A of 1%.

The strontium-nickel phosphate and its method of preparation aredisclosed in detail in US. Pat. 3,541,172, which is incorporated hereinby reference.

The following examples are intended to illustrate but not limit theinvention. Parts or percentages are given in moles unless otherwisespecified.

EXAMPLE 1 Strontium-nickel phosphate catalyst, prepared and driedaccording to the methods disclosed in U .8. Pat. 3,541,172, was groundto pass a No. 12 screen. Ninety-eight parts by weight of the powder, 2parts of Cr O and 3 parts of graphite were blended together and formedinto 3 x ,4 inch pellets. The graphite lubricant was removed by roastingin steam (3700 v./v./h. STP) and air (450 v./v./h. STP) at 650 C. for 6hours. Thirty cc. of the pellets (30 g.) were packed into a 4 foot by 1inch diameter Vycor glass reactor having a inch diameter thermowellaxially positioned. The reactor was heated electrically to 375 C. and afeed gas was passed through the catalyst bed at a rate of ml. .perminute, which is equivalent to a space velocity of 200 v./v./h. Both thefeed and product gas samples were analyzed by gas phase chromatography.Tabulated below are data from this run.

Process Feed gas, eflluent,

mole mole Component percent percent Air-CIL-CO 0. 2 0. 3 Isobutane 2. 82. 9 8. 2 8.1

1,3-butadiene 0. 5 0. 4

It is noted that the catalyst action produces a 20% conversion of thel-butene to its isomer and that no appreciable amounts of isobutylenewere lost. Although the data shows a 1% reduction in the isobutylene, nodimers or trimers were present in the efiluent. If desired, the reactionmixture can be fractionated by conventional means and theisobutene-l-butene cut can be recycled through the catalyst untilsubstantially all the l-butene is converted to cis and trans Z-butene.

EXAMPLE 2 A series of runs was made in which the temperature was variedbut a constant space velocity of about 189 v./v./h. STP was maintained.The reactor and the catalyst were the same as described in Example 1 andthe feed composition was similar. Below about 235 C. there was noperceptible isomerization of l-butene to Z-butene.

3 Results obtained at 355 C. are compared with the feed gas compositionin the table below. e

Thus, at 355 C., the l-butene decreased from an initial concentration ofabout 15.5% to about 10.1% while the 2-butene increased to about 22.5%in the reaction efiluent. At 415 C. the l-butene decreased to about5.75% and the 2-butene increased 26% in the efiluent.

At a space velocity of about 200 and a temperature of about 440 C., thefeed begins to undergo cracking, as indicated by a decrease in yield ofZ-butene and an increase in methane production. Temperatures higher than440 C. and/ or lower space velocities at 440 C. enhance the cracking.

EXAMPLE 3 Percent conversion (Percent l-butene in feed)(1-butene inproduct) (Percent l-butene in feed) Reaction temp, C.

Composition:

L' ts 93. mm MWHQQQNON Cis 2-butene Butadiene Conversion, percent Thedata show that at the space velocity of these runs, conversion-ofl-butene to Z-buteneis at'its peakat a temperature between 310-410 C.and selectivity to 2-butone is greatest in the 310360 C. range.

What is claimed is:

1. A method of isomerizin l-butene to Z-butene comprising passing amixture of C hydrocarbons containing said butenes over astrontium-nickel phosphate catalyst, at a temperature of from about toabout 440 C. and at a space velocity of from about 25 to about 800v./v./h. (STP) with the proviso that as temperature increases, spacevelocity also is increased.

2. The method of Claim 1 in which the C mixture is a mixture ofl-butene, 2-butene, isobutylene and n-butane with only small amounts ofbutadiene.

3. The method of Claim 1 in which the temperature is from about 260 toabout 410 C. and the space velocity ranges from about to about 225v./v./h.

4. The method of Claim 1 in which, the space velocity ranges from aboutto about 200 v./v./h. and the temperature ranges from about 350 to about410 C.

5. The method of Claim 1 in which the catalyst contains up to about twoweight percent of Cr O 6. The method of Claim 5 in which the catalyst isin pellet form.

7. The method of Claim 5 in which the catalyst has a particle size offrom about 4-6 mesh.

References Cited UNITED STATES PATENTS 2,926,207 2/1960 Folkins et a]252-437 3,541,172 11/1970 Stowe et al. 2606 69 DELBERT E. GANTZ, PrimaryExaminer V. OKEEFE, Assistant Examiner 223 3 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,830, 870 Dated August 20, 1974 flMark A. Harter (deceased),'= John R.'1. Frost, Robert A. Stowe It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

I" 'FT Col. 2, line 31, delete "3700" and insert 3730-.

"first Col. 3, in the/Table, under the, heading "Component", the secondline, delete "Isobutene" and insert -Isobutane--.

Col. 3, in the second Table, under the heading "Reaction temp., C.",under the subheading "410" delete v the first four numbers, i.e., ".3","3.2", 8.4" and "9.4" and insert --==.4-, --3.4, --8.3--, -9.2--respectively.

Signed and sealed this 26th day of November 1974.

(SEAL) Attest:

MeGQY M. emsafim. c. MARSHALL DANN Attesting Officer Commissioner ofPatents

